Generating unoccupied orbitals within density functional theory (DFT) for use in GW calculations of quasiparticle energies becomes prohibitive for large systems. We show that, without any loss of accuracy, the unoccupied orbitals may be replaced by a set of simple approximate physical orbitals made from appropriately prepared plane waves and localized basis DFT orbitals that represent the conti...

In preparation for computational work with molecular orbitals written as linear combinaions of atomic orbitals, for first and second row atoms, we have developed a general procedure to parametrize linear combinations of Gaussian orbitals. We used a Gaussian transform, and a Gauss-Legendre quadrature, to express hydrogenic orbitals (with the correct long-range dependence for collisions) as contr...

In this study, the substituent effect on the electronic, spectroscopic properties and thermodynamic parameters of neutral and oxidized states of ferrocylidene acetophenone complexes was investigated by adopting the hybrid meta exchange-correlation functional of M06-2X. The frontier orbitals and the highest occupied molecular orbitals–lowest unoccupied molecular orbitals gaps of the substituted ...

The solution of the Hartree-Fock equations involves the iterative construction of the Fock matrix based on approximate molecular orbit& and the diagonal&&ion of that Fock matrix to obtain new approximations to those orbitals. A significant portion of this work is unnecessary, however, because the occupied molecular orbitals, which are required to construct the Fock matrix, represent a small fra...

Symmetrical charge-delocalized intervalence radical ions should not be described by the traditional two-state model that has been so successful for their localized counterparts. If they lack direct overlap between their charge-bearing units (M), their diabatic orbitals have an equal energy pair of symmetrized M-centered combination orbitals that are symmetric (S) or antisymmetric (A) with respe...

we have evaluated the nmr shielding tensors for a:t,g:c,a:u in watson-crick, and u-quartet. we have computed nmr shielding tensors at b31yp level by using 6-31g(d) basis set. we have compute anisotropy and asymmetry in a:t,g:c,a:u and u-quartet. the nmr shielding tensors were calculated using the giao method. the natural bonding orbital analysis (nbo) were performed. nbo calculation have been ...

Motivated by recent work in density matrix embedding theory, we define exact link orbitals that capture all quantum mechanical (QM) effects across arbitrary quantum mechanics/molecular mechanics (QM/MM) boundaries. Exact link orbitals are rigorously defined from the full QM solution, and their number is equal to the number of orbitals in the primary QM region. Truncating the exact set yields a ...

The four most stable C(s) conformers of glycine have been investigated using a variety of quantum-mechanical methods based on Hartree-Fock theory, density-functional theory (B3LYP and statistical average of orbital potential), and electron propagation (OVGF) treatments. Information obtained from these models were analyzed in coordinate and momentum spaces using dual space analysis to provide in...